C# WebRequest定义主体参数-C中的方法POST#

我有密码： var请求=

(HttpWebRequest)WebRequest.Create("http://www.dba.dk/ajax/vip/telephonenumber/gettelephonenumber/?externalid=1033601271");

            string stringData = "externalid=1033601271";
            var data = Encoding.ASCII.GetBytes(stringData);

            request.Method = "POST";
            request.ContentType = "application/x-www-form-urlencoded; charset=UTF-8";
            request.ContentLength = data.Length;
            var newStream = request.GetRequestStream();
            newStream.Write(data, 0, data.Length);
            newStream.Close();
            WebResponse response = request.GetResponse();
            MessageBox.Show(((HttpWebResponse)response).StatusDescription);
            response.Close();

有了这个，我从服务器收到了400个错误的请求。我想我需要定义请求主体：-我在firefox网络分析器上检查过它应该是这样的：externalId=1033601271&uu RequestVerificationToken=Xd5coguwXJArf6-5mqnl8ExoBpueltNPQ2Svflsfo6Fe5Maw4Voawt89NPEFJPONPPJEPDF5MVO1CZMBGQWA1KS2M8ZXMPJ0DNexCcrxChipf\U pBjP7lkRbt-rs9HrpHQ2

如何在代码中定义它？还有，如何从服务器读取对字符串变量的响应